The present invention generally relates to printers and more particularly, to an arrangement for detachably receiving a cassette containing photosensitive film sheets for use in a laser beam printer and the like.
Conventionally, in laser beam printers, X-ray cameras, etc. in which photosensitive film sheets are subjected to exposure of images so as to record the images, an arrangement is provided wherein a supply cassette for supplying the film sheets to an exposure portion and a take-up cassette for receiving the film sheets having been subjected to exposure are, respectively, formed with outlet and inlet openings. In order to eliminate erroneous exposure of the film sheets, the outlet and inlet openings are, respectively, provided with light shielding covers for selectively covering and uncovering the outlet and inlet openings only when the film sheets are fed out of the outlet opening and into the inlet opening, respectively. However, the known apparatuses have certain in the case where the cassette is taken out of the apparatuses and when the light shielding cover uncovers each of the outlet and inlet openings, erroneous exposure of the film sheets takes place.
In order to prevent such erroneous exposure as described above, there has been proposed, for example, in Japanese Patent Laid-Open Publication No. 10733/1983 (Tokkaisho 58-10733), an X-ray camera including a cassette receiving arrangement for detachably receiving, through an aperture, a cassette formed with an opening for film sheets. The cassette receiving arrangement includes a door for selectively covering and uncovering the aperture, while the cassette includes a cover for selectively covering and uncovering the opening. It is so arranged in the known cassette receiving arrangement that when the aperture is covered by the door, the door is automatically locked and that when the opening of the cassette is covered by the cover, the door is automatically unlocked. However, the prior art cassette receiving arrangement has a disadvantage in that since the locking and unlocking operations of the door are electrically controlled, on the basis of detection signals indicating that the opening of the cassette is covered or uncovered by the cover, etc., it is impossible to take the cassette out of the aperture when electric power is not supplied to the prior art cassette receiving arrangement. Namely, when electric power is not supplied to the prior art cassette receiving arrangement due to service interruption, mechanical failures, etc., the film sheets cannot be taken out of the opening of the cassette. In other words, the known cassette receiving arrangement has such a serious drawback that the film sheets cannot be supplied to or taken out from the cassette.